Aside from their direct anti-cancer effects, HDIs boost the immune system by increasing the expression of the major histocompatibility complex (MHC) class I and II proteins, as well as costimulatory and/or adhesion molecules such as CD80, CD86, human leukocyte antigen (HLA)-DR, HLA-ABC, and intracellular adhesion molecule-1 (ICAM-1,28). Here, CD80 is linked to cancer.